Although hydrogen is the fuel of choice for fuel cells, its widespread use is complicated by the difficulties in storing the gas. Many hydrogen carriers, including hydrocarbons, metal hydrides, and chemical hydrides are being considered as hydrogen storage and supply systems. In each case, specific systems need to be developed to release the hydrogen from its carrier, either by reformation as in the case of hydrocarbons, desorption from metal hydrides, or catalyzed hydrolysis from,chemical hydrides and water.
The advantage of fuel cell power systems over batteries is that they are readily refuelable, and therefore can contain a “replaceable” fuel cartridge, and a “permanent” power module. A hydrogen fuel power system for small applications should ideally be compact and lightweight, have a high gravimetric hydrogen storage density, and be operable in any orientation. Additionally, it should be easy to match the control of the system's hydrogen flow rate and pressure to the operating demands of the fuel cell.